(CNN) – Six groups supporting Democratic candidates announced on Tuesday that their combined 2011 fundraising topped $19 million, according to one of the groups, American Bridge 21st Century.

The amount is significantly less than the $51 million fundraising number reported earlier in the day by American Crossroads and Crossroads GPS, the groups' counterparts supporting Republican candidates.Follow the Ticker on Twitter: @PoliticalTicker

The numbers are perhaps a disappointment compared to their projections in the spring of last year when they planned on being directly competitive with the opposition groups in fundraising. But the election season for Democrats has yet to heat up in earnest, and Democrats expect these fundraising numbers will increase dramatically once a Republican nominee emerges.

In super PAC disclosure filings due on Tuesday, four of the six organizations reported 2011 fundraising of $13.8 million. The other organizations, American Bridge 21st Century Foundation and Priorities USA, are legally designated as 501(c)(4) committees, and subject to filing regulations separate from those of PACs and super PACs.

The largest single fundraising haul was from Priorities USA Action, which grossed $4.4 million in 2011. The committee spent almost $2.9 million, and ending the year with no debt and $1.5 million cash on hand. The group reported donations totaling $1 million from the Service Employees International Union.

One of the groups, American Bridge 21st Century, reported raising $3.7 million and spending almost $2.9 million over the year. It ended the year with $839,256 cash on hand and $293,458 in debt. The committee's largest gift came from the American Federation of State, County, and Municipal Employees, which gave American Bridge $275,000.

House Majority PAC, which supports Democrats running in congressional races, announced fundraising of $3 million, ending the year with almost $1.2 million cash on hand and zero debt. The organization's most significant gift came from the Laborers' Political League.

That organization's Senate candidate counterpart, Majority PAC, spent just over half of its almost $2.7 million in fundraising. The committee reported $123,406 in debt and $1.3 million cash on hand. James H. Simons, a New York philanthropist donated $500,000.

Some of the organizations have been active in the GOP nominating contests, including the Priorities committee, which was behind advertisements in Iowa and Florida critical of Mitt Romney.